London: Oil and gas export revenue of the Organisation of the Petroleum Exporting Countries (Opec) rose by 12 per cent to a record $730 billion in 2007 as oil's extended rally had the group pumping nearly flat out, an Opec report showed on Thursday.

With no let up in the bull run - crude prices are up close to 50 per cent since the start of the year - 2008 should be another revenue record-breaker for Opec.

The world's biggest oil exporter, Saudi Arabia earned $206 billion last year from petroleum exports - a rise of 9.6 per cent on 2006, Opec said in its Annual Statistical Bulletin.

Boom times continued in other Opec countries as oil neared $100 a barrel towards the end of 2007.

The Opec report revised figures for previous years to include Ecuador and said the group's resources increased in 2007.

Reserves grew to 939 billion barrels from 927 billion in 2006, the report said, mainly reflecting an increase in Venezuela.

A strain on the world's oil refineries has fed into the rise in oil prices and the Opec report showed capacity in member countries was steady on last year at 9.34 million barrels per day.

Opec's natural gas reserves rose to 91 trillion cubic metres, up by 1.8 per cent from 2006.

However, Opec yesterday warned of growing uncertainty over demand for its oil in the years ahead, raising doubts whether multi-billion-dollar investments in new supply will be needed.

Opec, in its 2008 World Oil Outlook, said demand for its oil could fall to 31 million barrels per day (bpd) in 2012, below current production, as additions to supply excluding Opec crude outpace growth in demand.

The outlook underscores Opec's concern about moves in Europe and the US to cut oil dependence and promote alternatives. Any investment shortfall would worry consumer nations facing record oil prices.

"Without the confidence that additional demand for oil will emerge, and without reliable market signals, the incentive to invest can be affected," Opec secretary-general Abdullah Al Badri wrote in the report.

"Just like anyone else, oil producers do not want to invest in a product that will not be used."